Just takes some imagination. I would generally expect a good unique idea from anyone who does an alt Saber. A alt Gilgamesh would make more sense to me because he is a lot more evil then the Epic of Gilgamesh makes him seem. Even writing an alt version of that more true to the story would still show some similarity to Nasu Gil. I can see your argument and I'm not trying to persuade you against it. I personally wouldn't do an alternate since I generally like most of the servants in both Fate/Stay Night and Zero.